Definition: You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.
Input: Question: A and B can together finish a work in 40days. They worked together for 10days and then B left. After another 12days, A finished the remaining work. In how many days A alone can finish the job?

 Option A: 10

 Option B: 25

 Option C: 60

 Option D: 16

 Option E: 20

Option D